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I know that getting a smooth final cut/finish cut is hard.

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jbmauser

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I know it is tool shape and carriage speed (i think). I can't seem to figure out a tool profile to get a smooth finish.
 

ttabbal

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What's the nose radius on the tool you're working with?
 

benmychree

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A lubricant is important too, I use magic tap.
 

mikey

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Hey JB, maybe show us your tool? I bet the guys can get your sorted quickly.
 

jbmauser

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Thanks all. I spent last night viewing videos on youtube and realize my radius is probably at fault. I need to grind a new tool this morning and apply what I learned and also apply a solvent. I may be back..... thanks again.
 

GoceKU

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I agree with all the suggestions above, but i've had good luck with a fast feed rate, this requires lots of power from the lathe and good size tool but. I've gotten reflective surface finish with 400rpm and a fast feed but my lathe has 13,5 hp motor, you can try this metod and see if it works for you.
 

stupoty

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I agree with all the suggestions above, but i've had good luck with a fast feed rate, this requires lots of power from the lathe and good size tool but. I've gotten reflective surface finish with 400rpm and a fast feed but my lathe has 13,5 hp motor, you can try this metod and see if it works for you.
I find cast iron likes a high feed rate.

(13.5hp is a beast of a motor btw) ;)
 

ttabbal

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First and foremost, actually can't believe no one asked what material are you attempting to cut ?

Sure, but if you use a threading tool, it doesn't really matter what you're cutting, it's not going to be smooth. :)

At least, I think so, but I'm happy to learn how I'm wrong about it. Always willing to learn something new.
 

mikey

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Thanks all. I spent last night viewing videos on youtube and realize my radius is probably at fault. I need to grind a new tool this morning and apply what I learned and also apply a solvent. I may be back..... thanks again.
Finish has more to do with the material (anything is better than 1018 mild steel), speed, feed and the lead angle of your tool than the nose radius. The nose radius is important but not as important as you might think. Smaller nose radii are usually better than large radii for a lot of reasons. The tool geometry and sharpness of your edges also have a bearing.

Care to show us your tool?
 

P. Waller

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This may be counter intuitive but try taking the finish cut at 3-4 times the roughing spindle speed, if roughing at 300 Rpm's turn the spindle up to 1200 Rpm's for the finish cut, you will not be disappointed.
 

jbmauser

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I have been shaping and reshaping and it is getting smoother on a stainless steel rod not great but improving. I dug into the odd tools I inherited and found a carbide tool with a radical sideways angle and after seeing a video on a shear tool I figured that is what it is. I dressed it with a diamond stone and it gave me the best cut yet .... with solvent a bit of WD40. I will narrow my radius further as I guess it is still an oval and I am finishing it it my Tormek water stone grinder to get the best finish on the cutting edge and radius.
 
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